Location-based services such as location-based advertisement, location-based entertainment and location-based
personal assistant are emerging business applications that demand location-based mobile triggers. Location triggers
are standing spatial triggers. Similar to time-based triggers that are used to remind us of the arrival of a future
reference time point, location triggers are set on a spatial location of interest which subscribers of the trigger
will travel to at some future time instant.

Companies or merchants may use location triggers to support location-based advertisements;
for example, Bloomingdale may send a 20% sale coupon to its medallion member
shoppers who are located within five miles of its stores. Individuals use location-based triggers to set up
personal reminders indicating the arrival of a spatial location of interest.

For instance, a user could set a spatial alarm on her mobile client, which alerts her whenever she is
nearby some dry clean store or her favourite grocery store in her neighbourhood, reminding her to pick up or
drop her dry cleaning items or automatically retrieve her stored grocery shopping list.